1. Field of the Invention
The present invention relates to power supplies for use in electrical devices, and, more particularly, to a power supply keying arrangement for an electrical apparatus.
2. Description of the Related Art
An electrical apparatus, such as an ink jet printer, typically requires a power supply to convert alternating current (AC) power, such as that available at a wall outlet at a user's home or office, to direct current (DC) power at a DC voltage level and current level suitable for use in the electrical apparatus. It is known to provide both internal and external power supplies for such an electrical apparatus.
For example, an ink jet printer having an internal power supply typically requires the user to simply attach an electrical cord from an AC connector located at the AC input of the internal power supply to an AC wall outlet. An advantage of the internal power supply is that it is easy for the user to apply electrical power to the printer. One disadvantage, however, is that if the printer power supply fails, then the entire printer must be sent to a service center for repair.
An ink jet printer having an external power supply typically requires the user to attach the DC output of the external power supply to the DC input of the ink jet printer and attach the AC input of the power supply to the AC wall outlet. An advantage of the external power supply is that in the event of a power supply failure, the power supply unit can be replaced without having to send the entire printer in to a service center for repair. However, typically, replacement of the power supply is limited to an exact replacement of the power supply.
What is needed in the art is a power supply keying arrangement for an electrical apparatus that permits a range of downwardly compatible power supplies to be used in the electrical apparatus.